The invention relates to improvements made to transducer devices for reading or writing information on a magnetic support. It relates more particularly to such transducer devices which have an insulating plate on the surface of which are arranged in thin layers on the one hand a magnetic material forming a magnetic circuit comprising a narrow air gap whose plane is substantially parallel to that of the said surface and on the other hand a single turn of a conducting metal having a zero or substantially zero magnetic permeability and which fills at least in part the said air gap.
Such transducer devices are used more particularly as magnetic heads which are to serve for the reading or writing of binary information, in the form of magnetisation in one direction and in the opposite direction, on tracks of planar discs covered with a magnetic material.
In a known device of this type (IBM Technical Disclosure Bulletin, Vol. 13, No. 2, July 1970, pages 562-564) used to form a magnetic head of the type mentioned hereinbefore, the single turn of conducting metal forms an open circuit. Thus for writing information on a planar disc covered with a magnetic material it is necessary to directly apply to the terminals of this single turn in open circuit, high intensity pulses generally of the order of 1 ampere in order to create in the magnetic circuit having a narrow air gap a magnetic field of sufficient intensity to induce magnetisation on the tracks of a magnetic disc arranged underneath the said air gap. During the reading of information on a magnetic disc by means of such a head, the magnetic flux resulting from the passage of a magnetized portion of a disc track underneath the air gap of the magnetic circuit induces a low voltage of the order of 100 microvolts in the open circuited singleturn. Therefore, the contacts and circuits associated with a head of this type are difficult to make. Moreover, the low value of the reading signal induces at the single turn terminals can be a significant source of errors during the reading of information written on the magnetic disc.
A solution which has been proposed for obviating these difficulties is to produce these magnetic heads by placing in thin layer form several turns of conducting metal in the air gap of magnetic circuit. However, it is particularly difficult and onerous to produce such a magnetic head.